HI
I've got 2 voltages wich change relative to each other with speed and diameter.
Any suggestions of a circuit to devide them to get a relative output eg.
8v/4v=2v
4v/2v=2v
or
8v/2v=4v
4v/1v=4v
Thanks

 

What are the voltage sources? (Will a resistive divider load them down?)
What is the divided output feeding? (will the output load down the resistive divider?)
What accuracy do you need? (10%, 5%, 1% ?..so you can choose available values of resistors for the divider)

Or a simple way would be potentiometer(s) with one end tied to your voltage source, the other end tied to common, and the output between the wiper and common. Adjust as needed.

Ken

 

1st voltage comes from paper speed 0v at standstill to 8v at full speed.
2nd voltage comes from paper roll speed, at full speed with full roll 0.5v to 3.6v at end of roll.
Need to determine roll size from vairables,.

 

Are you thinking something like two digital readouts (voltmeters that a read the scaled down voltages) or something that actually calculates the roll size automatically...and does something with the result?

What I ask my customers to do is describe that vision in their head, and we can then fill in the stuff between what they have and what they want.

Ken

 

Analog Approach
I would use pair of logarithmic amplifiers on the inputs, subtract one from the other, and run the result through an exponential amplifier.

Digital Approach
Use A/D converters to get the values into digital form. Do the division. Output the result to a display or other control actuator.

Either one will work. What kind of time and budget are we talking about?